Cell Cycle Mitosis And Meiosis

Cell Cycle Mitosis And Meiosis

Cell cycle mitosis and meiosis - The term "mitose", coined by Walther Flemming in 1882, comes from the Greek word μίτος (myth, "warp wire"). There are several alternative names for this process, for example, "karyokinesis" (nuclear division), a term introduced by Schleicher in 1878, or "division of equality", proposed by August Weismann in 1887. However, the term "mitose" is also used in the broader sense of some authors, to refer to calcinosis and cytokinesis. Currently, "division of equations" is most commonly used to refer to meiosis II, the part of meiosis that most likes mitosis.

Mitosis is part of the cell cycle when replicated chromosomes are separated into two new nuclei. Cell cycle mitosis and meiosis - Cell division gives rise to genetically identical cells in which the number of chromosomes is maintained. In general, mitosis (nucleus division) is preceded by phase S of interphase (where DNA is replicated) and is often accompanied or followed by cytokinesis, which divides cytoplasm, organelles and membrane cells into two new cells containing almost parts identical to that cellular component.

The mitosis process is divided into several steps related to the completion of a set of activities and the beginning of the next. Cell cycle mitosis and meiosis - These stages are prophase, prometaphase, metaphase, anaphase, and telophase. During mitosis, duplicated chromosomes, condense and adhere to shaft fibers, which pull a copy of each chromosome to the opposite side of the cell.

Mitosis occurs only in eukaryotic cells. Prokaryotic cells, which have no nucleus, are divided by a different process called binary fission. Mitosis varies between organisms. For example, animal cells suffer mitosis "open", where nuclear envelopes are damaged before the separation of chromosomes, while fungi suffer mitosis "closed", where chromosomes divide into intact cell nuclei. Cell cycle mitosis and meiosis - Most animal cells undergo deformation, known as rounded mitotic cells, to adopt morphology of the nearby sphere at the beginning of mitosis. Most human cells are produced by mitotic cell division. Important exceptions include sperm gametes and ova produced by meiosis.

Many descriptions of the cell division were made during the 18th and 19th centuries, with varying degrees of precision. In 1835, German botanist Hugo von Mohl described the cell division in green algae Cladophora glomerata, which states that cell multiplication occurs through cell division. In animal cells, the cell division with mitosis was found in frogs, rabbits and cat cornea cells in 1873 and was first described by Polish histologist Waclaw Mayzel in 1875.

Cell Cycle Mitosis And Meiosis

Considering that meiosis is a form of eukaryotic cell division that produces haploid or gamete sexual cells (which contain a single copy of each chromosome) from diploid cells (which contains two copies of each chromosome). This process takes the form of DNA replication followed by two successive nuclear and cellular divisions (Meiosis I and Meiosis II). As in mitosis, meiosis is preceded by a DNA replication process that turns each chromosome into two sister chromatids.

Errors in meiosis resulting in aneuploidy are the main cause of known abortion and the most common genetic cause of developmental abnormalities. In meiosis, DNA replication is followed by two rounds of cell division to produce four child cells, each with half the number of chromosomes of the original stem cells.

Homologous chromosome pairs (bivalent) are arranged in double rows along with the metaphase plate. The arrangement of paired chromosomes in relation to the spindle equipment poles is random along the metaphase plate. This is the source of genetic variation through random variations because paternal and maternal chromosomes in homologous pairs are similar, but not identical. The number of possible settings is 2n, where n is the number of chromosomes in the haploid set. Humans have 23 different chromosomes, so the number of possible combinations is 23, which is more than 8 million.

During this period, homologous chromosomes pair and undergo genetic recombination, a programmed process in which DNA can be cut and then repaired, allowing them to exchange part of their genetic information. The subset of recombination events results in a crossover, which creates a physical connection known as chiasmata between homologous chromosomes.

Cell cycle mitosis and meiosis - In most organisms, this relationship can help direct each pair of homologous chromosomes beyond meiosis I, producing two haploidéis that have half the number of chromosomes as stem cells. During Meiosis II, cohesion between sister chromatids is released and they are separated from each other, as during mitosis. In some cases, the four meiotic products form gametes, such as sperm, spores or pollen. In females, three of the four meiotic products are usually removed by extrusion in the polar body, and only one cell develops to produce eggs. As the number of chromosomes is halved during meiosis, gametes can merge (i.e., fertilization) to form diploid zygotes. which contains two copies of each chromosome, one from each parent. Thus, alternating cycles of meiosis and fertilization allow sexual reproduction, with subsequent generations maintaining the same number of chromosomes.